Eric Johnson and Dan Goldstein have published an investigation of the effect of policy defaults on organ donation in the journal Science[Download]. Defaults determine whether a citizen is in the organ donor pool unless they choose not to be (an “opt out” system, as in some European countries) or is not in the organ donor pool unless they choose to be (an “opt in” system as, in the United States). Looking at real-world data from a variety of European countries in addition to experimental data, it is found that most people stick with the default category they are assigned to.

Across European countries the opt out countries have drastically higher proportions of the population in the potential organ donor pool: a difference of 60 percentage points minimum.

Does the size of the donor pools matter? Johnson and Goldstein find that opt out countries are home to more organ transplantation, and presumably lives saved. This is supported by a regression analysis that controls for religion, educational level, and medical infrastructure.